Archive for the Spacecraft Design category

The Canadian Satellite Design Competition (CSDC) is a Canada-wide competition for teams of university students (undergraduate and graduate) to design and build low-cost satellite. The CSDC plans to subject the satellites in competition to full space qualification testing, and to launch the winning satellite into orbit to conduct science research. The CSDC is modeled after existing university engineering competitions, such as those sponsored by the National Aeronautics and Space Administration (NASA) or the Society for Automotive Engineers (SAE).

The winning teammates are members of Space Concordia, a student-run astronautical engineering association based in the Faculty of Engineering and Computer Science at the Concordia University in Montreal. The selection process was conducted by industry experts at the David Florida Laboratory of the Canadian Space Agency in Ottawa, a highly secured facility where commercial and research satellites from the United States and Europe are routinely tested. From twelve teams that initially entered the competition, Space Concordia Team was among only three to go for final testing. Alex Potapov, Mechanical Team Lead, answered a few questions about the Space Concordia cubesat mission.

Q: What is the scientific payload for the mission you are designing?A: Our mission is to study the south Atlantic anomaly, more on that here. We plan on doing this by detecting high energy particles present in the region. Our spacecraft is equipped with a Geiger Counter operating in its proportional mode. This will allow us to determine not only the amount of radiation but also the type of particle present.

Q: What hardware do you intend to use? Off-the-shelf boards and software or are you developing your own?A: Most of our components are of the shelf with the exception of several printed circuit boards. One of the more impressive and less accessible pieces of hardware is the Xiphos Q6, which is a sophisticated FPGA that will be used as the central computer of our satellite. The software is developed internally, and it is based on the Linux operating system.

Q: How do you intend to communicate with your satellite from the ground? UHF, Iridium modem, etc.?A: The spacecraft will communicate with a ground station located near Montreal by means of an antenna that is capable of transmitting and receiving at UHF and VHF armature frequency bands. At this orbit we will have a communication window of about 10-11 min per pass. The communication system was entirely developed by Tiago Leao, PhD Candidate at Concordia University.

Credit: Space Concordia Team

Q: How do you generate and store power onboard the satellite? Batteries, solar panels? Do you intend to use deployable solar panels?A: The satellite is equipped with four solar arrays made of 6 ultra high efficiency solar cells each, these cells charge 4 lithium ion batteries. The solar cells are mounted to the body panels of the spacecraft and are not deployable. The entire power system was designed and developed by Ty Boer, an electrical engineering student at Concordia University.

Q: Does the attitude determination and control system rely solely on reaction wheels? How do you intend to unload them? Magnetorquers, cold gas thrusters, or have you developed a novel technique?A: Our approach to ACS does not require any of the above, the philosophy behind the cubesat was to keep it as simple as possible and still perform its mission, therefore a passive ACS system was selected. The system contains of permanent magnets and hysteresis rods, this will allow us to remain stable through communication window. We also have sun sensors for telemetry data.

Q: Do you plan to have any orbit control systems onboard? What is the orbital profile of the mission?A: No, there is no active orbit control on-board. The flight software has a look up table that it uses to determine the spacecraft position, this table is updated through TLE data. We then use this position to execute certain commands such as power on the transmitter to establish communication.

Credit: Space Concordia Team / Concordia University

Q: How do you plan to control the temperature onboard the satellite?A: The satellite has a passive cooling system, and active heaters that keep critical components such as the batteries within operating range. Cooling is controlled by careful design of conductive elements and optical surfaces.

The second Canadian Satellite Design Competition (CSDC) team that answered our invitation to a Q&A is the team from Dalhousie University. Colin Oâ€™Flynn, graduate student at Dalhousie University and CTO of the CSDC team, answered our questions.

Q: What hardware do you intend to use? Off-the-shelf boards and software or are you developing your own?A: We are aiming to use COTS boards and software as much as possible, especially during development. Eventually we will be forced to design and build custom hardware, since there is a very specific form-factor which many COTS boards wonâ€™t fit inside. Weight is also a huge issue for us â€“ since many COTS boards contain lots of features we might not need (e.g.: LCD display, Ethernet connector), we can shave some weight by spinning our own board and not wasting space or weight with those features.

Ideally though weâ€™ll just adapt the COTS board design to our satellite, meaning we can use a tested design with minimal work. Not Invented Here (NIH) syndrome is dangerous to engineering projects, so while our current research does show we canâ€™t find the correct form factor, weâ€™ll always be checking the market for new products that might let us avoid needless designs and builds.

Q: How do you intend to communicate with your satellite from the ground? UHF, Iridium modem, etc.?A: Again our satellite has slightly different objectives from a normal commercial satellite, which are primarily concerned with issues such as maximizing bandwidth or minimizing lag, since that gives the best return on investments.

In our project we also want to provide something with a wide scientific and public appeal. To that end we plan on using amateur radio frequencies â€“ this means people around the world can track our satellite. Often amateur radio operators are on the lookout for interesting projects which introduce young students to radio communications. Letting students receiver data from a real satellite overhead does a lot to promote both amateur radio and space, which just maybe will help inspire the next generation of engineers.

Whether this will be in the S-Band or just UHF hasnâ€™t been finalized yet, although there is potential to actually have a beacon running in the more common UHF, and our more bandwidth-intensive comms (e.g.: for downloading payload data) in S-Band. The actual coding technique will use more recent codes (e.g.: turbo or LDPC). Again since this is supposed to be a more ‘innovative’ approach to space, we are working with some of the respected professors and students in our department to get recent advances in both coding and antenna design on our spacecraft.

Q: How do you generate and store power onboard the satellite? Batteries, solar panels? Do you intend to use deployable solar panels?A: The solar panels will not be deployable, but fixed on the outside surface, with batteries storing the charge. This area will use more mature technology. The power system is so critical, and since testing the components such as panels or batteries for the required environmental conditions is beyond our capabilities, we donâ€™t want to rely on experimental designs.

Q: Does the attitude determination and control system rely solely on reaction wheels? How do you intend to unload them? Magnetorquers, cold gas thrusters, or have you developed a novel technique?A: The satellite is very small; many Cubesats only use magnetorquers without reaction wheels. This limits what and where you can correct obviously, so we are still exploring more interesting techniques. We have “penciled in” reaction wheels and magnetorquers, but this could drastically change.

The attitude determination is also planned to be pretty standard. Due to the small size of sensors on the market, we actually plan on outfitting our satellite with a wide range of sensors beyond what is required for attitude determination. We plan on adding a three-axis magnetometer, gyro, and accelerometer, along with GPS receiver. The idea is to provide enough data for postprocessing on Earth for testing new algorithms, experiments, etc.

Q: Do you plan to have any orbit control systems onboard? What is the orbital profile of the mission?A: Nothing planned yet; the orbit we are given is defined as:

Launch details wonâ€™t be confirmed for some time, so some of this is mostly chance depending what we end up riding along with.

The only possible orbit control system we are investigating would be for deorbiting the satellite at the end of its life. Space is a shared resource, and we want to make sure we arenâ€™t needlessly polluting it with our satellite. If it naturally will deorbit in a reasonable time this wonâ€™t be necessary, but itâ€™s something we want to be sure of.

Credit: Dalhousie CSDC Team

Q: How do you plan to control the temperature onboard the satellite?A: Currently something we are investigating. Preliminary calculations show we can do this passively to keep things within acceptable limits. Other Cubesats have done this in practice too.

We are trying to use automotive grade parts when possible, which gives us a better temperature range to work with. Understandably this isnâ€™t possible for everything; the solar cells and battery are one obvious example.

Q: Who are the members registered with your team? What areas of expertise do they represent? A: Itâ€™s a huge range of skills we have, including over a quarter that arenâ€™t engineers or scientists. Our team is pushing outreach in the community, so for example running programs to introduce kids to space exploration, and the idea that itâ€™s something they could become involved in themselves. Other sections of the team such as marketing, management, and finances are critical to our success, but have nothing to do with the core technical designs.

The technical team has about ten core members. The number of people working on the project though will be higher: we are defining senior year projects, which students will be able to get credit hours for. Time is always a problem in student run projects, so we are trying to make sure people get credit for all this work. Or as I like to point out: once they agree to help, they have to help, because otherwise they will fail the senior year project! Itâ€™s one way of retaining “volunteers”.

Dr. Mason Peck, head of the Space Systems Design Studio at Cornell University, answered a few questions for OrbitalHub readers about the Sprite spacecraft. Peck earned a B.S. in Aerospace Engineering from the University of Texas at Austin, and his M.S. and Ph.D. at UCLA as a Howard Hughes Fellow.

A team at the Space Systems Design Studio focuses on Sprite, a simple, feasible design of spacecraft systems printed on small wafers of silicon. This design packages traditional spacecraft systems onto a single silicon microchip.

DJ: Miniaturization brings along quite a few limitations: small payloads and data storage, and much less power available. Why pursue miniaturization when designing a spacecraft?Mason Peck: In fact, I would disagree with the word–and the concept of–miniaturization. It implies that the goal is to shrink an existing space-system architecture or technology here. Instead, the goals are the following:

– Start from the bottom and work up, i.e. from the level of fundamental technologies, and find out how little it might take to create a space system. If we start by focusing on a mission and consider the problem from the top down, or if we merely try to implement an existing solution at a smaller scale, we miss out on lots of opportunities for innovation.

– Without prejudice, ask how we explore at this small scale? Specifically, how does a very tiny spacecraft exploit the physics of the solar system to navigate, reorient, scavenge power, and the other housekeeping tasks that are fundamental to space exploration.

– And then, with this basic technology concept in place, ask what missions are possible? This approach is known sometimes as “technology push,” where the availability of some new function or performance motivates a new sort of exploration.

So, we expect to discover a kind of parallel universe of exploration possibilities, which has remained hidden from us because of our parochial view of what a spacecraft consists of. I’ll give you some examples in response to your third question.

DJ: How far can miniaturization go?M.P.: One of our most surprising discoveries is that commercial, off-the-shelf electronics components for mainstream contemporary applications like cell phones and iPods are vastly superior in performance to typical spacecraft electronics. Most people understand that spacecraft electronics are several generations behind the state of the art, and for good reasons such as needing radiation-hard parts, flight-proven reliability, etc. But what’s astonishing is just how far ahead consumer electronics are. We’ll be able to implement GPS-based orbit knowledge, radio communications, and attitude sensing all on about 1 cm^2 of integrated circuitry, using catalog components that anyone can buy. And they’re remarkably cheap, mostly because they’re made in the millions: single-chip GPS receivers, little CMOS cameras, etc. are no more than a few $ each in some cases.

The reliability or survivability of these off-the-shelf components is certain to be much poorer than flight-qualified parts. However, remember that at this scale of size and cost, fabricating and launching thousands or millions is entirely within reach. A single ChipSat may be unreliable, but the cloud of them may offer very high reliability. More than that, a cloud can be understood statistically, with notions like “statistical confidence,” which are very hard to come by when one is building a single, exquisite spacecraft.

A ChipSat will never replace Hubble, but it would not be expected to do so. Instead, ChipSats would form the basis of exploration missions that benefit from a large number of distributed, although coarse, measurements. More generally, this notion of “technology push” introduces a transformative idea for scientists. Instead of posing a science mission that presupposes a spacecraft architecture, let innovation in mission-science objectives couple with engineering innovation. That’s how we’ll do new, remarkable things.

DJ: Can you give some examples of mission scenarios envisioned for swarms of Sprite spacecraft?M.P.: One of my favorites is that a Sprite may be able to enter a planetary atmosphere without parachutes, rockets, or a heat shield, and yet never burn up. Some of our early work on this problem for Earth’s atmosphere suggests that a 25 micron thick Sprite can reenter without burning up and maintain a cool enough temperature that electronics can continue to operate. So, reentering Sprites can sample the ionosphere, the mesosphere, and on down to the surface of the Earth. We’d get unprecedented measurements of spatial and temporal phenomena like turbulence and particle densities.

Another idea is to place a cloud of these Sprites between the Earth and the Sun, maybe at a so-called Lagrange point, which would be a sort of orbital equilibrium between the two. Each Sprite in the cloud would have the simple task of transmitting a single bit when solar-wind flux or magnetic flux exceeded some threshold, indicating a solar storm. This data would offer a distributed measurement for science, but at least as important it would provide a new type of advance warning of these storms, which can knock out radio communications on Earth.

Yet another application is a bit of science fiction, but it gets us thinking along new lines. Consider a particle accelerator. On Earth, these systems accelerate charged particles like electrons to relativistic velocities so that physicists can study subatomic phenomena. Now imagine the Sprite as a particle. It would be electrostatically charged, like a toy balloon on a dry day, and in that way resembles a very large electron. Could we build a kind of particle accelerator to launch Sprites out of the solar system at very high speed? The Navy already has a railgun that uses electromagnetic effects to launch large masses. Their recent successes show that the concept is perfectly sound. In fact, if you could direct the energy of their 30 kg railgun into a, say, 30 mg Sprite, that’s a factor of 1000 higher speed. Such a Sprite could be the first interstellar explorer. Michio Kaku and I have discussed the wild notion of a ring-shaped Sprite accelerator on the moon or in Jupiter’s orbit (in fact, the idea appeared on his Sci Fi Science TV show). In principle, such a launch system could send a Sprite to the nearest star system in a few decades.

DJ: The small mass and size of a Sprite spacecraft does not leave much room for radiation shielding. Especially during deep space missions, single events can take a spacecraft out of commission. How can Sprite spacecraft compensate for these inherent hazards of space travel?M.P.: Absolutely right. Radiation will degrade the Sprite until it stops functioning. The easiest solution is simply to produce a rad-hardened chip. They’re not uncommon, although it’s expensive to design and build them. But it can be done, and amortizing that cost over millions of Sprites would make doing so a lot more appealing than how it’s done now, where we go to all that effort for a relatively small number of chips. But if you don’t want to get into rad hardening, remember that this effect is a statistical one. So, using a large enough number of Sprites for a mission would be a way to ensure that a desired fraction of them survive, even though a large number would fail. Again, we could design in this statistical reliability. And the more you use, the more reliably the mission meets its objectives.

DJ: Sprite is by definition a propellantless spacecraft. What type of propulsion can be employed?M.P.: I wouldn’t be against trying to implement traditional propulsion at this scale. In fact, it’s been done, with mixed success. But the reason to pursue propellantless technologies is that chemical propulsion does not scale down well.

We find that several approaches do scale well. First, solar sailing is a clear winner. With a thin but still rigid silicon wafer, we can get performance benefits similar to the vast solar sails that have been proposed, but with the important advantage that the sail is not a floppy mess, difficult to deploy and steer around. The acceleration of a solar-sail Sprite increases with 1/L, where L is the length scale. As long as there are no limitations on thickness, a uniformly shrunken solar sail works better than its larger analogue. For example, a 1m solar sail accelerates 10x as fast as a 10m solar sail, as long as the thickness scales proportionately. That proportionate scaling may be tough to achieve, but what’s easy is the stiffness: a 25 micron Sprite is stiff enough that it needs no deployable booms or trusses, and it’s therefore effectively thinner (less mass for the area) than the larger sails.

A little harder to implement but even more intriguing is electrodynamic tether technology. Sprite sends a current through a wire that extends from the spacecraft, grounded in the ionospheric plasma. The current interacts with the Earth’s magnetic field, like the windings in an electric motor, producing a force. That force can accelerate the spacecraft. Just like the solar-sailing example, an ED tether is a lot more convenient when it’s shorter: it’s basically a rod, not a floppy string. The dynamics-related problems that the Space Shuttle tether experiments encountered would not arise here.

DJ: How many Sprite spacecraft are currently deployed and what kind of payloads do they have?M.P.: There are three prototypes on the outside of the International Space Station. They’re not free-flying. They’re self-powered with solar cells, and they have their own on-board computers, radios, and other circuitry. They are their own payload in the sense that if they communicate, we’ll be able to confirm that Sprite’s unique communications architecture is a valid design. We didn’t have time (and we had no money, in fact) for a science payload per se.

DJ: Swarms of hundreds of decommissioned Sprite spacecraft orbiting the Earth could make mission flight control rooms very nervous. Are there any post-mission disposal methods considered for Sprite missions?M.P.: Yes and no. Space debris is certainly a risk, but Sprites do not have to be debris. In low-earth orbit, their unique flight dynamics mean that aerodynamic drag very quickly pulls them back into the atmosphere. Specifically, a 325 km orbit would decay in about 2 days. Even at 500 km, they would reenter in weeks, at most. If they burn up, that’s that. If they don’t, it’s because they’re so delicate that they would never hurt anyone even if one were to land on a person on the ground. So, they clean up after themselves.

DJ: What are the areas with room for improvement in the design and manufacturing of chip-sized satellites?M.P.: The next step will be that the design will transition from discrete parts to a single, application-specific integrated circuit (ASIC). That’s the real objective. It would be far lighter, less power-hungry, and more maneuverable than the current prototypes on ISS.

â€¦ or to be more exact, the cheese re-entered the Earthâ€™s atmosphere and performed a successful splashdown in the Pacific Ocean onboard SpaceXâ€™s Dragon spacecraft on December 8, 2010. The same day, roughly three and a half hours earlier, the Dragon spacecraft was placed into low Earth orbit by a Falcon 9 launch vehicle, which lifted off from Cape Canaveral Air Force Station Space Launch Complex 40 on COTS Demo Flight 1.

On this flight, several key components of the Dragon spacecraft were tested: the Draco thrusters, which control the spacecraft throughout flight and reentry; the PICA-X heat shield, which is the SpaceX variant of NASAâ€™s phenolic impregnated carbon ablator (PICA) heat shield; avionics; telemetry; and the drogue and main parachutes used for stabilization and landing.

The Dragon spacecraft is capable of fully autonomous rendezvous and docking, can carry over three metric tons in each of the pressurized and unpressurized sections, and it supports five to seven passengers in crew configuration. SpaceXâ€™s primary goal for this demo flight was to collect as much data as possible.

Before the launch, Elon Musk, SpaceX CEO and CTO, made the following statement:

“When Dragon returns, whether on this mission or a future one, it will herald the dawn of an incredibly exciting new era in space travel. This will be the first new American human capable spacecraft to travel to orbit and back since the Space Shuttle took flight three decades ago. The success of the NASA COTS/CRS program shows that it is possible to return to the fast pace of progress that took place during the Apollo era, but using only a tiny fraction of the resources. If COTS/CRS continues to achieve the milestones that many considered impossible, thanks in large part to the skill of the program management team at NASA, it should be recognized as one of the most effective public-private partnerships in history.”

In 2007, projections of sea level rise made by the Fourth Assessment Report of the Intergovernmental Panel on Climate Change were in the range of 28–43 cm by 2100, but there are new projections of the sea level rise that are in the order of 1.4 m.

While the trend is quite obvious, it is very important to be able to make accurate predictions.

Cryosat has been designed to measure the ice thickness on land and also at sea, and will provide enough data so that a precise rate of change of the ice thickness can be determined. A better understanding of how the volume of ice on Earth is changing will also be possible.

The declared primary goals of the CryoSat mission are to determine the regional trends in Arctic perennial sea-ice thickness and mass, and to determine the contribution that the Antarctic and Greenland ice sheets are making to mean global rise in sea level. Cryosat will also measure the variations in the thickness of Earthâ€™s polar caps and glaciers. The spacecraft will be operational for a minimum of three years.

Credits: ESA/P. Carril

The spacecraft has a launch mass of 720 kg, of which 23 kg is the fuel required for orbital maneuvers and attitude corrections. The overall size of the spacecraft is 4.6 m x 2.34 m. Two solar panels are attached to the spacecraftâ€™s body and provide a maximum of 800 W of power. As the CryoSat-2 orbit is not Sun-synchronous, providing enough power to the scientific payload has been a considerable challenge.

The operational orbit will be a 717 km non Sun-synchronous orbit with a 92 degree inclination.

The primary payload of the CryoSat-2 spacecraft is the SAR/Interferometric Radar Altimeter (SIRAL). In order to have the position of the spacecraft accurately tracked, a radio receiver called Doppler Orbit and Radio Positioning Integration by Satellite (DORIS) and a laser retro-reflector are part of the payload as well. A global network of laser ranging stations (the International Laser Ranging Service or ILRS for short) will support the mission. Three star-trackers will ensure a proper orientation of the spacecraft.

Using the Synthetic Aperture technique, CryoSat-2 measurements taken by SIRAL will have a 250 m resolution in the along-track direction. The instrument is designed to operate in three measurement modes: Low Resolution Mode (LRM) mostly over the oceans, Synthetic Aperture Radar (SAR) mode over sea-ice areas, and SAR Interferometric (SARIn) mode over steeply sloping ice-sheet margins, small ice caps, and mountain glaciers.

Credits: ESA – AOES Medialab

CryoSat-2 will be placed in orbit by a Dnepr launch vehicle. With a lift-off mass of 211 tons, Dnepr is 34 m long and 3 m in diameter, and has three stages that use hypergolic liquid propellants (N2O4 nitrogen peroxide and UDMH unsymmetrical dimethylhydrazine). In addition, there are Dnepr configurations with a third and a fourth stage for missions that require more energy. The launch vehicle is based on an ICMB designated as SS-18 Satan by NATO. The development and commercial operation of the Dnepr Space Launch System is managed by the International Space Company (ISC) Kosmotras. Dnepr can lift 4,500 kg to low Earth orbit (LEO) or 2,300 kg to a 98 degree Sun-synchronous orbit. Among other satellites launched by Dnepr are Demeter, Genesis I, Genesis II, and THEOS. Dnepr, carrying Cryosat-2, will lift off from Baikonur Cosmodrome in Kazakhstan.

The European Unionâ€™s Global Monitoring for Environment and Security (GMES) initiative was born as the result of a growing need for accurate and accessible information about the environment, the effects of climate change, and civil security. GMES uses as its main information feed the data collected by satellites developed by ESA. Data is also collected by instruments carried by aircraft, floating in the ocean, or located on the ground.

GMES provides services that can be grouped into five main categories: land management, marine environment, atmosphere, aid emergency response, and security.

There are five Sentinel missions designed as components of the GMES initiative. These missions will complement the national initiatives of the EU members involved. The missions will collect data for land and ocean monitoring, and atmospheric composition monitoring, making use of all-weather radar and optical imaging. Each of the Sentinel missions is based on a constellation of two satellites.

Sentinel-1 is an all-weather radar-imaging mission. The satellites will have polar orbits and collect data for the GMES land and ocean services. The first satellite is scheduled for launch in 2012. Sentinel-1 will ensure the continuity of Synthetic Aperture Radar (SAR) applications, taking over from systems carried by ERS-1, ERS-2, Envisat, and Radarsat. Sentinel-1 satellites will be carried to orbit by Soyuz launch vehicleslifting off from Kourou.

Sentinel-2 will provide high-resolution multi-spectral imagery of vegetation, soil, and water, and will cover inland waterways and coastal areas. Sentinel-2 is designed for the data continuity of missions like Landsat or SPOT (Satellite Pour lâ€™Observation de la Terre). Each satellite will carry a Multi-Spectral Imager (MSI) that can ‘see’ in thirteen spectral bands spanning from the visible and near infrared (VNIR) to the shortwave infrared (SWIR). The first Sentinel-2 is planned to launch in 2013. Vegawill provide launch services for Sentinel-2 missions.